JACKSON, Miss. (WLOX/AP) — A National Transportation Safety Board member says the Texas tour bus hit by a freight train was not supposed to have taken the road where it got stuck at a rail crossing.

WLOX-TV reports NTSB Board Member Robert Sumwalt says during a news conference the driver may have followed a GPS set for commercial vehicle use rather than directions from a Florida-based tour company.

The crash killed four Texan tourists aboard the bus and injured dozens more.

Sumwalt says there were actually three buses transporting passengers from Bay St. Louis to Biloxi as part of a tour organized by Diamond Tours. All three buses were set to leave around the same time and travel to Boomtown Casino Tuesday afternoon. Only one of the buses was operated by Echo Tours, and that was the one involved in the deadly accident.

All three bus drivers received directions that sent them up Caillavet Street, not Main Street. Sumwalt says the Echo bus didn’t follow those directions, and instead used a GPS set for commercial vehicle use.

NTSB investigators on Thursday did a sight distance test to determine at what point an obstruction on the tracks is identifiable to the people on the train. Sumwalt says there was clear visibility and no surprises.

An NTSB highway engineer is surveying the grade of the road and the geometry of the hump the bus got stuck on before Tuesday’s crash.

The investigation team still hasn’t interviewed the bus driver, but still expect to do so. They say they were very busy interviewing the train crew first.

The bus driver and the train crew members all took a drug test immediately after the crash.

The NTSB team will be in Biloxi through the beginning of next week.

Earlier Thursday, a Texas attorney announced he has filed a lawsuit in state court against the railroad, the bus company, and its unidentified driver. Attorney Mikal Watts is working for the son of Peggy Hoffman, one of the four crash victims. Another attorney, Broadus Spivey, is also suing separately for the heirs of Hoffman’s husband, Ken.

The lawsuit filed Wednesday says CSX Transportation allowed “ultra hazardous” conditions at the crossing, and the Echo Transportation driver failed to follow traffic signs. Neither company responded immediately to requests for comment.

Mayor responds to safety concerns

The mayor of Biloxi says he’ll work with the railroad to close some crossings and make others safer.

Mayor Andrew “FoFo” Gilich says he’ll use recommendations from CSX Transportation to minimize the chances of another fatal wreck.

The city had already scheduled a hearing March 21 to discuss closing six railroad crossings when the CSX freight train hit a bus stuck on the tracks Tuesday. However, the Main Street crossing, where 40 were injured in addition to the deaths, isn’t on the closure list.

The National Transportation Safety Board is investigating.

The crossing has a warning sign about low clearance, topped by a picture of a tractor-trailer stuck on a railroad track.

Moments before the deadly crash

A survivor of the deadly bus crash in Mississippi says she was sitting right behind the driver when the bus became lodged on a railroad crossing.

Justine Nygren of Austin, Texas, says the driver yelled for everyone to get off, but stayed on the bus himself, trying to ensure that people did leave.

Speaking in a telephone interview from her home, Nygren says she left through the front door of the bus and walked a short distance alongside the tracks, not looking back. She tells The Associated Press while she was walking, the train hit the bus and pushed it past her.

Nygren says the rest of her memory is a fog.

Nygren says another bus returned her and other uninjured survivors Wednesday night to Bastrop, Texas.